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    <meta charset="UTF-8">
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    <title>Document</title>
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<body>
    <script>
        'use strict';
        var num=10;
        console.log(num);
        delete num;
        function fn(){
            console.log(this);
        }
        fn();

        function Star(){
            this.sex = '男';
        }
        var ldh = new Star();
        console.log(ldh.sex);

        setTimeout(function(){
            console.log(this);
        },2000);

        function fun(a,a){
            console.log(a+a);
        }
        fun(1,2);
    </script>
</body>
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